<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>无标题文档</title>
<style>
#div1{ width:100px; height:100px; background:red; position:absolute;}
#div2{ width:100px; height:100px; background:yellow; position:absolute; left:100px;}
#div3{ width:100px; height:100px; background:blue; position:absolute; left:200px;}
#div4{ width:100px; height:100px; background:green; position:absolute; left:300px;}
</style>
<script>

//组件开发 : 多组对象，像兄弟之间的关系( 代码复用的一种形式 )

window.onload = function(){
	
	var d1 = new Drag();
	d1.init({    //配置参数
		id : 'div1'
	});
	
	var d2 = new Drag();
	d2.init({   //配置参数
		id : 'div2'
	});
	
	bindEvent(d2 ,'toDown',function(){
		document.title = 'hello';
	});
	
	bindEvent(d2 ,'toDown',function(){
		document.body.style.background = 'black';
	});
	
	var d3 = new Drag();
	d3.init({    //配置参数
		id : 'div3'
	});
	
	bindEvent(d3 ,'toDown',function(){
		document.title = '妙味';
	});
	
	bindEvent(d3 ,'toUp',function(){
		document.title = '课堂';
	});
	
	var d4 = new Drag();
	d4.init({    //配置参数
		id : 'div4'
	});
	
	bindEvent(d4 ,'toUp',function(){
		document.title = 'byebye';
	});
	
};

function Drag(){
	this.obj = null;
	this.disX = 0;
	this.disY = 0;
	
	this.settings = {   //默认参数
		
	};
	
}
Drag.prototype.init = function(opt){
	
	var This = this;
	
	this.obj = document.getElementById(opt.id);
	
	extend( this.settings , opt );
	
	this.obj.onmousedown = function(ev){
		var ev = ev || window.event;
		This.fnDown(ev);
		
		fireEvent(This , 'toDown');
		
		document.onmousemove = function(ev){
			var ev = ev || window.event;
			This.fnMove(ev);
		};
		document.onmouseup = function(){
			This.fnUp();
			
			fireEvent(This , 'toUp');
			
		};
		return false;
	};
	
};

Drag.prototype.fnDown = function(ev){
	this.disX = ev.clientX - this.obj.offsetLeft;
	this.disY = ev.clientY - this.obj.offsetTop;
};
Drag.prototype.fnMove = function(ev){
	this.obj.style.left = ev.clientX - this.disX + 'px';
	this.obj.style.top = ev.clientY - this.disY + 'px';
};
Drag.prototype.fnUp = function(){
	document.onmousemove = null;
	document.onmouseup = null;
};


function bindEvent(obj,events,fn){
	//obj : 楼层
	//events : 书架
	//fn : 一本书
	
	obj.listeners = obj.listeners || {};
	obj.listeners[events] = obj.listeners[events] || [];
	
	obj.listeners[events].push( fn );
	
	if(obj.nodeType){
		if(obj.addEventListener){
			obj.addEventListener(events,fn,false);
		}
		else{
			obj.attachEvent('on'+events,fn);
		}
	}
}

function fireEvent(obj,events){   //主动触发自定义事件
	
	if(obj.listeners && obj.listeners[events]){
		for(var i=0;i<obj.listeners[events].length;i++){
			 obj.listeners[events][i]();
		}
	}
	
}


function extend(obj1,obj2){
	for(var attr in obj2){
		obj1[attr] = obj2[attr];
	}
}


</script>
</head>

<body>
<div id="div1"></div>
<div id="div2"></div>
<div id="div3"></div>
<div id="div4"></div>
</body>
</html>
